Magnetic bearings of this type are known. In a magnetic bearing described by McHattie, see Review of Scientific Instruments, Vol. 12, pp. 429-435, 1941, with which small rapidly rotating steel cylinders are suspended contactlessly and which is equipped with axially active electromagnetic stabilization, radial vibrations of the suspended rotor are transmitted by contactless magnetic coupling to a radially movably mounted needle and damped by partial immersion of the needle in oil. Oil damping is also specified by J. W. Beams in "Double Magnetic Suspension", Review of Scientific Instruments, Vol. 34, pp. 1071-1074, 1963.
Disadvantages of this damping system are the necessary encapsulation of the movably mounted stator part to prevent oil losses, the additional assembly volume of the device necessitated by the encapsulation, and the associated relatively high manufacturing costs. As a component of mass-produced magnetic-bearing systems intended to compete directly with cost-optimized roller-bearing systems, especially in the use of such bearings for textile spindles and centrifuges, the oil damper appears to be unfavorable because of its manufacturing cost alone. Furthermore, because of circulation of part of the oil mass, the characteristics of an oil damper correspond only within limits to the characteristics of an ideal vibration damper with damping force proportional to speed, since mass acceleration forces caused by the oil circulation also become active in addition to the pure damping force.